Projection display systems use spatial light modulators (“SLMs”) to modulate light from a lamp to produce high-quality images suitable for home theater, large-format front projectors, such as digital cinema, projectors for business conferences, and rear-projection television. The resolution of such systems is related to the number of picture cells (“pixels”) that the SLM generates. The image from the SLM is magnified and projected onto a display screen. Generally, a larger SLM will generate more pixels than a smaller SLM with similarly sized actuator cells. Conversely, if the size of the actuator cell is reduced, an SLM of a fixed size can generate more pixels. However, SLMs suitable for large-format displays might not have suitable resolution for other applications, such as medical imaging, satellite imaging, or other display applications requiring very high information content.
A viewer typically sits relatively far back from a large-format display screen, where the viewer's eye smooths the pixellated image. Unfortunately, the resolution acceptable for large-screen displays might not be suitable for high-resolution displays, where the viewer is relatively close to the displayed image and a higher information density is desired. One technique to provide a high-resolution image is to provide SLMs with more actuator cells, either by making a larger SLM chip or by reducing the size of the actuator cells. Unfortunately, both approaches adversely affect yield-per-wafer and cost.
Multiple SLMs have been used in image display systems for various reasons. One technique overlays images from multiple SLMs to increase the brightness of the resultant image. Another technique interleaves images from multiple SLMs that control different colors of light operating at a reduced duty cycle (e.g. 50% duty cycle when using two SLMs). Using multiple SLMs allows the use of slower SLMs to achieve a higher apparent refresh rate, but does not increase the resolution of the display.